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Author Topic: Wi-Fi power output for wireless routers and PC's?  (Read 5378 times)
KC8CXZ
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Posts: 85




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« on: March 04, 2009, 06:34:02 AM »

I often wondered what the frequencies and power output is for home/public 'hotspot' routers as well as a typical notebook/netbook PC, or other mobile device like iTOUCH?  Are we talking just a few mW, or several hundred mW?  Or even a watt or more?  What kind of internal antenna does such a notebook/netbook PC have in order to communicate with a Wi-Fi router/network?  Just curious.  Thanks!
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K5DVW
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Posts: 2193




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« Reply #1 on: March 04, 2009, 06:57:19 AM »

Most operate around 2.5 Ghz ISM band. They put out roughly 20 dBm +/- 3dBm average power. Peak power is about 10dBm higher than that. At 5.8 GHz about the same, but not much 5.8 GHz out there now.
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N3OX
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« Reply #2 on: March 04, 2009, 06:58:07 AM »

"Are we talking just a few mW, or several hundred mW?"

Somewhere in there... +19dBm, about 79mW, is a pretty typical maximum output power for cards I'm finding on Google for 802.11g.

The actual power output changes with time depending on the needed signal strengths.

I found some routers listed as doing 400mW.

If you want actual hard limits, I think you're going to have to dig in the IEEE 802.11 specifications.

"What kind of internal antenna does such a notebook/netbook PC have in order to communicate with a Wi-Fi router/network? "

I took apart a T41 thinkpad with a dead screen, and it had a pair of small printed circuit antennas.

As luck would have it, they're selling some on eBay:

http://tinyurl.com/dylmub

The other one is a little different.

The other one is mounted vertically along the side of the screen, and the one in the picture is mounted horizontally along the top, and presumably the WiFi transceiver uses a diversity system to select the better one.

There's a huge variety of antennas in wireless devices; the routers probably use pretty conventional collinear types, but I haven't really taken many of those apart :-)  A lot of PCMCIA laptop cards (before they built antennas into every laptop) used printed circuit antennas right on the main board of the card.

73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KB3LSR
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Posts: 297




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« Reply #3 on: March 04, 2009, 06:58:38 AM »

WiFi (802.11b/g) is in the 2.4GHz range.  The power output of the cards and routers is ~ 100mW.  If you wanted to, you could unencrypt your network, claim it as a ham station (by setting your SSID to broadcast your callsign) and run all the way up to 1.5kW since the 2.4 GHz spectrum is shared with the amateur bands.

There have been a lot of amateur experiments with WiFi and I remember reading a QST article a year or so ago where they got 50+ miles off of WiFi.
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KB0VWG
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Posts: 9




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« Reply #4 on: March 04, 2009, 07:07:24 AM »

Typically most Routers that you buy off the shelves at Walmart or Best Buy etc, They have an output power of 28mw. Linksys is one of those that are set at that power level. There is firmware that you can upgrade your routers power up to 250mw, but running your router at power output will eventually burn it up. I have dd-wrt firmware in my router for over a year now and I run my router at 100mw all the time so I can supply my parents with internet across the field. The firmware that I use in my router does not work on all routers, need to check the website for info. www.dd-wrt.com
 There are more exspensive routers out there that run 500mw to 1 watt of power but they are in hundreds of dollars range.73s
Michael
kb0vwg
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WA3SKN
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Posts: 5437




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« Reply #5 on: March 04, 2009, 01:11:15 PM »

The handbook now covers WiFi in one of the later chapters.  It is interesting reading.
73s.

-Mike.
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N8EKT
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Posts: 371




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« Reply #6 on: March 04, 2009, 02:30:14 PM »

Even unlicensed access points are limited to 1 watt max.

The ONLY license holders in the 902-928mhz, 2.4ghz and 5.8ghz bands are hams.
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KB0NPW
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Posts: 62




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« Reply #7 on: March 05, 2009, 01:52:09 PM »

This is highly interesting to me, because I am getting ready to build a high gain antenna for just this purpose. I live out in the sticks and can't get any faster than 28.8k on dialup. It is terrible! A friend who is also a ham lives just 3 miles away as the crow flies and he has DSL.

Has anyone on here ever tried to build one of those cantennas like from Amateur Logic TV? I saw plans on another style that I am thinking of building which uses an old DirecTV dish and a Linksys adapter. I realize I will have to find a way to extend the USB cable to get it from outside into the shack.
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KB0NPW
Member

Posts: 62




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« Reply #8 on: March 05, 2009, 03:55:15 PM »

Here is the antenna I am thinking of building:
http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/
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KE6ANM
Member

Posts: 17




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« Reply #9 on: March 06, 2009, 07:01:19 PM »

your friend who is three miles away should have no problem hitting you with an average wifi set up and a yagi.
here in the Mojave desert I get my wifi on 2.4 ghz at 500 mw over 22 miles away, no problem, with a lawn chair type grill dish.
Look for a small pc card wifi set up like a orinoco gold card with an external antenna connection, or a high power 300 mw buffalo card, with an external antenna connection and a pig tail and a  yagi.( a cheapy tv rotor is even better.
3 miles is nothing to worry about.
The cards and antennas are for sale on ebay as a kit every day. good line of site is better.
good luck
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